Small patches need greater protection

Clearing of mulga in central Australia. Conservation activities in heavily cleared landscapes focus on keeping the remaining large patches intact, often disregarding the increasingly important role of smaller patches in conserving biodiversity. (Photo by Michelle Venter)

Small patches of native vegetation are critically important to biodiversity conservation and need greater protection from clearing according to a new analysis undertaken by Ayesha Tulloch and colleagues. Just because a patch of native vegetation might be small, doesn’t mean we can afford to lose it.

The researchers examined historical and current patch-size distributions to evaluate how important small patches are to different ecosystems. Using data on vegetation clearing in Australian, they calculated the historical change in the contribution of small patches to overall extent.

“We found that many vegetation communities in Australia now occur disproportionately in small patches,” says Tulloch. “At least 22% of major vegetation communities have over half of their remaining extent in patches smaller than 1,000 hectares. For some communities the loss of patches as small as 1 hectare would be catastrophic – for others it would make very little difference to persistence at all.”

The researchers point out that many vegetation communities (such as Brigalow and Mulga in Queensland) are exposed to the double jeopardy of high loss and high fragmentation. These communities are currently undergoing increased clearing as a result of changes to clearing laws that allow clearing of land deemed to be of ‘high agricultural value’. (See Decision Point #76)

“The long-term consequence of not accounting for the role of all vegetation patches is the continuous erosion of small patches in highly fragmented vegetation communities and the slow, inevitable decline of vegetation communities and the species dependent on them,” says Tulloch. “Our approach is the first to explore the consequences of small-scale vegetation clearing due to the failure of current policies to protect vegetation patches smaller than a given threshold.”